Method of manufacturing an electric battery

ABSTRACT

In an electric battery comprising a plurality of interconnected cells within an insulating casing, internal connections between the cells and to external terminals are provided by a member which is preformed as a single unitary conducting member, secured in the casing while still in unitary form and subsequently severed in situ in the casing to form a plurality of separate connections.

BACKGROUND OF THE INVENTION

The invention relates to electric batteries and to methods ofmanufacturing the same. The invention is particularly applicable toelectric batteries of the type which comprise a plurality of individualdry cells which are located within a casing and electrically connectedtogether to form a battery.

Standard dry cells are well known and commonly comprise cylindricalunits having an output voltage of about 1.5 volts. It is also known toassemble a plurality of such cells in a common battery casing withappropriate series or parallel connections between the cells so as toprovide a suitable electrical output at battery terminals.

Commonly, the battery is provided with external terminals and thebattery casing is provided with internal connections to interconnect thecells with each other and with the external battery terminals. One sucharrangement is shown, by way of example, in British Patent SpecificationNo. 1331800.

Problems do however arise in providing suitable internal electricalconnections within the battery casing. Previous proposals have involvedthe use of soldered wire joints or separate spring contacts which haveto be fitted individually into position in the battery casing. Thebatteries have to be capable of withstanding shock and previousproposals have included pouring a suitable blocking material into thecasing once the cells have been located in position so as to preventmovement of the battery cells. These previous proposals are inherentlylabour intensive in their construction and therefore expensive.Furthermore, the use of soldered joints and materials, such as bitumen,to hold the cells in place in the battery, tend to lead to theintroduction of dirt during assembly.

It is an object of the present invention to provide improved internalconnections within such a battery and an improved method ofmanufacturing such internal connections.

SUMMARY OF THE INVENTION

The present invention provides an electric battery comprising aninsulating casing, a plurality of individual cells located within saidcasing, a pair of external terminals for effecting electrical connectionto the battery, and a plurality of internal connections forinterconnecting the cells with each other and with the externalterminals, said internal connections being preformed as a single unitaryconducting member, secured in position in the casing while still inunitary form, and subsequently severed in situ in the casing to form aplurality of separate internal connections.

In this way, the relative positions of the internal connections arepredetermined by the manufacturing operation of the single unitaryconducting member and provided the single unitary conducting member isaccurately located in position in the casing, the separate internalconnections will be accurately located in their respective positionswithin use of a labour intensive assembly process.

In a preferred embodiment, the single unitary conducting member islocated on the inside of a lid of the battery casing.

Preferably the internal connections include a plurality of springmembers arranged to engage the cells so that in the assembled battery,the spring members tend to retain the cells in a desired position.

Preferably the internal connections are formed from a single sheetmember of electrically conducting material. Preferably the sheet memberis formed of steel.

Preferably a plurality of securing means are provided in said batterycasing for attaching the single unitary conducting member to the casing,at least one securing member being provided for each part of the unitaryconducting member which forms a separate internal connection.

Preferably the internal connections are preformed on the unitaryconducting member by a sequence of stamping operation. In one preferredembodiment, a plurality of parts of the unitary conducting member arebent out of the plane of the member so as to form a plurality of contactarms.

The invention also provides a method of manufacturing a plurality ofinternal connections for an electric battery which method comprisesforming a plurality of internal connections on a single unitaryconducting member, securing the unitary conducting member in position inpart of a battery casing, and severing in situ in the casing the unitaryconducting member into a plurality of separate internal connections.

Preferably the plurality of internal connections are formed as a unitaryconducting member by a sequence of machining operations on a singlesheet of electrically conducting material. Preferably the machiningoperations include a succession of stamping operations. The machiningoperations may also include bending operations to form conducting arms.

Preferably the method includes securing the unitary conducting member ina part of the casing by a plurality of connecting means, at least oneconnecting means being provided for each part which is to be severed toform a separate internal connection.

Preferably the unitary conducting member is secured in a lid of abattery casing.

Preferably the severing is effected by stamping. The stamping may beeffected through the unitary conducting member and through part of thebattery casing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a battery according to the present inventionwith the lid removed,

FIG. 2 is a plan view of the battery of FIG. 1 with the lid in position,

FIG. 3 is an underplan view of the battery lid showing the cellpositions in broken lines,

FIG. 4 shows a conducting member used to form internal connections inthe battery,

FIG. 5 is an underplan view of the battery lid prior to fixing themember shown in FIG. 4,

FIG. 6 is a view similar to that of FIG. 5 showing the conducting memberof FIG. 4 in position, and

FIG. 7 shows a manufacturing sequence used for making the member shownin FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The battery shown in this example is of generally similar type to thatdescribed in British Patent Specification No. 1331800. In other words,it comprises an insulating casing containing four 1.5 volt dry cellswhich are interconnected to each other and to two external batteryterminals by means of internal connections in a lid of the batterycasing.

As shown in FIG. 1, the battery comprises a box-like casing 11 whichhouses four cylindrical cells 12. The casing 11 is provided withinternal partition walls 13 which form four generally rectangularcompartments 14, each of which houses a respective one of the cells 12.The battery casing and partition walls 13 are formed of insulatingmaterial and in this case thermoplastic plastics material. Each of thecells 12 is of conventional construction one terminal of which isprovided by the casing of the cell and the other is provided by acentral electrode 15 at its upper end. FIG. 2 shows the lid 16 of thecasing. This is similarly formed of thermoplastics plastics material andhas two external battery terminals 17 and 18 which form the negative andpositive terminals respectively and each comprises a helical springconnected through the lid by a rivet.

In order to interconnect the cells in the battery and to connect them tothe external terminals 17 and 18, a plurality of internal connectionsare provided on the lower face of the lid 16. The internal connectionsmay be arranged to provide series, parallel or series parallelconnections. In the particular example which will now be described, theinternal connections provide series connections between the cells.

All the internal connections are preformed on a single unitaryelectrically conducting member shown in FIG. 4. This is made by asequence of operations which will now be described with reference toFIG. 7. FIG. 7 shows stages A to F of the manufacturing operation. Asingle plain strip 20 of electrically conducting material, which in thisexample comprises steel, is subjected to a succession of formingoperations. As shown in FIG. 7, each stage of operation is carried outby a press tool and at stage A, a plurality of locating holes 21 areformed through the sheet together with two generally rectangularapertures 22. At stage B, a subsequent operation of the press tool formsfurther enlarged apertures through the sheet material. At stage C, thepress tool forms more extensive apertures. At stage D, the edges of someprojecting parts are upturned out of the plane of the sheet material asindicated at 23. At stage E, a machining operation is carried out tobend certain projecting arms along the broken lines marked 24 so thatcertain parts of the conducting sheet form inclined arms projecting outof the plane of the sheet. At stage F, the press tool carries out apiercing operation to separate the unitary conducting member 26 from thestrip. The separated member is then as shown in FIG. 4.

The lid is moulded so that the under face has the formation shown inFIG. 5. This includes downwardly projecting arcuate ribs 27 at eachcorner which are adapted to fit into the open upper end of the casingshown in FIG. 1. A plurality of downwardly projecting pegs 28 areprovided and these are arranged to engage the locating holes 21 referredto in FIG. 7. A central aperture 29 and a further aperture 30 areprovided for the passage of the rivets which hold the external terminals17 and 18. A plurality of downwardly projecting stop members 31, 32, 33and 34 are provided. Additionally, securing projections 35 are providedat four positions on the under face of the lid. The projections 35 arearranged to engage the upper edges of the partition walls 13 shown inFIG. 1. Two supporting ribs 36 are provided on opposite sides of theaperture 30 and are arranged to support the arms of the clip 44 when inposition thereby preventing excessive opening of the arms.

In assembling the battery, the conducting member 26 is preformed as aunitary member as already described with reference to FIG. 7 and is thenassembled in the lid of the casing as shown in FIG. 6. The steel plateis positioned with the holes 21 fitting over the projecting pegs 28. Thepegs are then heat staked to retain the conducting plate 26 in position.Once the plate is securely positioned, the plate is severed, in situ inthe lid, so as to separate the various internal connecting members. Thesevering is carried out by a piercing operation at the positions marked37 in FIG. 3. This piercing is effective through the plate forming theconducting member 26 as well as the plastics lid 16. This has the effectof separating the conducting plate into five separate internalconnecting members each of which is secured to the lid by two of thepegs 28. In this way, each of the separate internal connecting membersis accurately positioned in the lid although only one single locatingoperation was necessary. This simplifies production and it ensures thateach of the individual internal connecting members is accuratelypositioned and cannot be either misplaced or omitted.

The positions of the separate cells 12 in relation to the internalconnections has been shown in broken lines in FIG. 3. Contact member 40interconnects the central terminal of cell 46 to the casing of cell 47.Contact member 41 connects the central terminal of cell 47 with thecasing of cell 48. Contact member 42 interconnects the central terminalof cell 48 with the casing of cell 49. Contact member 43 provides aU-shaped clip 44 which engages the central contact of cell 49 andprovides a connection through the connecting rivet to external terminal18. The central contact member 45 connects the casing of cell 46 to theexternal terminal 17 through the rivet securing the terminal 17.

The projections 31 and 32 on the underside of the lid provide stopmembers which limit the extent of axial movement of the cells within thebattery when completed. The projections 33 and 34 carry out the sameeffect for the other two cells but additionally they provide a lateralguide for the long conducting arms of the contact members 40 and 42.

When the plate has been secured in the lid and the severing operation iscarried out, the terminals 17 and 18 are secured by passing the rivetsthrough holes 29 and 30 in the lid and corresponding holes 50 and 51 inthe contact members 44 and 45. A plastic disc is positioned between theterminal 17 and the upper face of the lid 16 so as to cover thepiercings in the plastic lid caused by the severing operation of thecontact members from the conducting plate 26.

Due to the bending operations carried out in stage E of FIG. 7, thevarious internal contact members are provided with spring arms whichengage the cells so as to maintain good electrical contact with thecells while accommodating minor variations in positioning of the cells.

It will be appreciated that by use of the above method of forminginternal connections within the battery, the assembly procedure isgreatly simplified and there is no need to solder or weld the intercellconnections. Furthermore, the sequence of assembly operations is muchreduced.

Once the lid has been completed as shown in FIG. 3, the lid is locatedin position on the lower part of the casing shown in FIG. 1 and the twoare sealed together by ultrasonic welding. During this operation, theprojections 27 become secured to the upper edges of the lower casingwall and the projecting members 35 on the underside of the lid 16 becomewelded to the upper edges of the partition walls 13 in the lower part ofthe casing.

The invention is not limited to the details of the foregoing example.

We claim:
 1. A method of manufacturing a plurality of internalconnections for an electric battery having a casing with a plurality ofcell compartments for housing individual cells, which method comprisesforming on a single unitary conducting member a plurality of internalconnections having contact members for abutment with said cells so as toform electrical contact therewith, securing the unitary conductingmember to part of the battery casing so that the contact members lie inpredetermined positions relative to the cell compartments, and severingin situ in the casing the unitary conducting member into a plurality ofseparate internal connections by stamping through the unitary conductingmember and simultaneously piercing through part of the battery casing.2. A method according to claim 1 in which the plurality of internalconnections are formed as a unitary conducting member by a sequence ofmachining operations on a single sheet of electrically conductingmaterial.
 3. A method according to claim 2 in which the machiningoperations include a succession of stamping operations.
 4. A methodaccording to claim 1 which includes securing the unitary conductingmember in a part of the casing by a plurality of connecting means, atleast one connecting means being provided for each part which is to besevered to form a separate internal connection.